1. Technical Field
The present invention relates to a monochromator and a charged particle beam apparatus including the same and, more particularly, to a monochromator (MC) for matching optical axes with a low cost and a charged particle beam apparatus including the same.
2. Description of the Related Art
A monochromator is an apparatus for supplying light of a narrow wavelength range and is optics/monochrome spectrometer for extracting desired monochromatic light by performing spectroscopy on white light through a combination of a lens and a slit. Such a monochromator is used optics in a charged particle beam apparatus or used as an energy analyzer. An example of a conventional monochromator is described below.
In relation to a Mollenstedt energy analyzer MA, FIG. 1 is a side cross-sectional view and plan view illustrating the Mollenstedt energy analyzer MA. As illustrated in FIG. 1, the Mollenstedt energy analyzer MA is a charged particle energy analyzer using the off-axis chromatic aberration of a cylindrical lens CylL. The cylindrical lens is a charged particle lens in which a rectangular opening is formed at the center of three electrodes 11, a high voltage is applied to the center electrode, and two electrodes on both sides are used as ground voltages. An insulating material 12 is provided between the three electrodes 11. Energy of electrons is decelerated almost close to 0 near the center electrode, a component that passes through the outside of the optical axis of the cylindrical lens is selected, and energy of charged particles is analyzed using an energy dispersion generated by the chromatic aberration of the lens axis. Such an energy analyzer is named the Mollenstedt energy analyzer MA by taking the inventor's name.
In relation to a monochromator using an electrostatic lens of FEI Co., Ltd., FIG. 2 is a diagram illustrating a monochromator of FEI Co., Ltd. As illustrated in FIG. 2, the monochromator of the FEI Co., Ltd. is a monochromator MC for selecting the off-axis component of an electron source by an aperture, passing the selected component through the outside of an electrostatic lens, and performing monochrome (i.e., enlarging or reducing energy) on the component by performing spectroscopy on the energy. The monochromator may be used in a charged particle beam apparatus, such as a scanning electron microscope (SEM). Such a monochromator can improve resolution of an image by reducing the influence of a chromatic aberration (Patent document 0001).
In relation to monochromators of Delft University of Technology, JEOL Co., Ltd., and Tubingen University, FIGS. 3 to 5 are diagrams illustrating the monochromators of Delft University of Technology, JEOL Co., Ltd., and Tubingen University. As illustrated in FIGS. 3 to 5, a Wien Filter type monochromator MC is mounted on the electron gun of a transmission electron microscope (TEM) or scanning transmission electron microscope (STEM), energy is subject to spectroscopy, and monochrome may be performed on the energy (i.e., an energy distribution may be reduced) (Patent document 0002 to 0004).
In relation to a monochromator of CEOS Co., Ltd., FIG. 6 is a diagram illustrating a monochromator of CEOS Co., Ltd. As illustrated in FIG. 6, a 4-stage electrostatic deflector is mounted on the electron gun of a transmission electron microscope (TEM) or scanning transmission electron microscope (STEM), energy is subject to spectroscopy, monochrome may be performed on the energy (i.e., an energy distribution may be reduced) (Patent document 0005). In accordance with the monochromator of CEOS Co., Ltd., there is an advantage in that resolution of an image is improved in an energy region of 60 keV or less that is lower than common 200 keV because the influence of a chromatic aberration is reduced. Furthermore, energy resolution in an electron energy loss spectroscopy (EELS) on the lower side can be improved.
3. Cited References    (Patent Document 001) Henstra, Charged Particle source with integrated energy filter, US8461525B2    (Patent Document 0002) Hindrik Willem Mook, Wien filter, U.S. Pat. No. 6,452,169 B1    (Patent Document 0003) Masaki Mukai, Method of adjusting transmission electron microscope, US2013/0248699 A1    (Patent Document 0004) Erich Piles, Monochromator for charged particles, EP1220292B1    (Patent Document 0005) Uhlemann, Monochromator and radiation source with monochromator, US2008/0290273A1